Electrostatic clamps or chucks (ESCs) are often utilized in the semiconductor industry for clamping workpieces or substrates during plasma-based or vacuum-based semiconductor processes such as ion implantation, etching, chemical vapor deposition (CVD), etc. Clamping capabilities of the ESCs, as well as workpiece temperature control, have proven to be quite valuable in processing semiconductor substrates or wafers, such as silicon wafers. A typical ESC, for example, comprises a dielectric layer positioned over a conductive electrode, wherein the semiconductor wafer is placed on a surface of the ESC (e.g., the wafer is placed on a surface of the dielectric layer). During semiconductor processing (e.g., ion implantation), a clamping voltage is typically applied between the wafer and the electrode, wherein the wafer is clamped against the surface of the ESC by electrostatic forces.
Most electrostatic clamps exhibit “sticking” behavior at one time or another, whereby a workpiece is retained against a surface of the ESC, despite the ESC not being powered. Sticking of a workpiece to the surface of an ESC is generally attributed to residual electrostatic charges at the interface between the ESC and workpiece not finding a rapid path to electrical ground after removal of power to the electrodes of the ESC. The nature, amount, and distribution of the residual charge is generally uncontrolled, since the phenomena that retains the charge is also generally uncontrolled and not well understood.
The retaining phenomena may vary daily or even hourly, as well as varying based on the particular ESC and workpiece lot undergoing clamping. The sticking behavior impacts throughput of workpieces through the system, and is therefore problematic.
Accordingly, a need exists in the art for an apparatus, system, and method for mitigating residual clamping of a workpiece to ESCs, while improving workpiece throughput and minimizing breakage of workpieces.